The present invention relates to methods of and apparatus for blocking lenses, and in particular to an improved method of and apparatus for applying a block to the surface of a lens to permit alteration of the lens.
Alteration of lenses includes both generating surfaces on lenses to impart specific optical properties thereto, and grinding or edging the peripheries of lenses to a predetermined outline. Surface generation commonly involves a series of steps. For example, the optical center, and optionally the cylinder axis, of a lens blank are located and marked on one face thereof. Next, a lens block is attached to the lens such that the optical center and cylinder axis of the lens are aligned with the center point and cylinder axis of the block. The desired optical properties are then generated upon the unfinished face of the lens by grinding the lens while supporting the same by means of the block.
Edging a lens to a desired peripheral outline involves a series of similar steps. For example, the optical center, and optionally the cylinder axis, of the lens are located. Next, a lens block is attached to the lens such that the optical center and cylinder axis of the lens are aligned with the center point and cylinder axis of the block. The lens and block are then gripped by a work holder of a lens edging machine, and the periphery of the lens is ground to a desired shape.
Whether a lens is to be surface finished or edged, machines for applying a lens block to the lens are well known in the art and referred to as "lens blockers". In use of such machines a lens block, which may carry an adhesive pad for being pressed against a lens to secure the block to the lens, is carried in a chuck of the machine. The lens is placed on the machine and, by means of targets and reference marks, is accurately visually aligned with its optical center and cylinder axis in a predetermined relationship with the center point and cylinder axis of the block. The block and lens are then moved together, either by moving the block against the lens or vice versa, to attach the block to the lens.
In a common arrangement, the lens is supported on a horizontal surface of the machine and the chuck is above the lens with the block extending downwardly therefrom. To prevent the block from falling out of the chuck, and yet to permit its release when it is affixed to the lens, it must be releasably retained by the chuck. Heretofore releasable mechanical retaining means have been employed, which have necessitated a relatively time consuming and dexterious manipulation of the block to position it in the chuck, both in order to accommodate the retaining means and by virtue of the fact that in conventional lens blockers, only a small spacing ordinarily exists between the chuck and the surface for supporting the lens. Lens blockers illustrative of the state of the art and having mechanical retaining means associated with the chucks thereof are illustrated in U.S. Pat. Nos. 4,227,349 and 4,229,911, issued to Bela J. Bicskei on Oct. 14, 1980 and Oct. 28, 1980, respectively.